Long-term evolution (LTE) wireless standards are being implemented in the unlicensed spectrum to meet demand from ubiquitous and bandwidth-hungry mobile services and applications. This is achieved through carrier aggregation by expanding the licensed spectrum to include unlicensed channels. However, unlicensed spectrum is currently dominated by consumer-grade wireless networks (e.g., WIFI). The centralized/synchronous access mechanisms used by LTE standards are incompatible with the distributed/asynchronous access mechanisms used by WIFI. In particular, LTE is not designed to yield the channel to WIFI and may potentially starve WIFI networks of bandwidth. In particular, whereas WIFI is distributed and asynchronous, LTE is centrally managed by the base station and synchronous. LTE does not recognize the presence of WIFI devices and will continuously schedule uplink and downlink transmissions, without yielding the channel for WIFI transmissions. WIFI will therefore stay in a constant backoff state and be starved of channel access.
While simple on-off duty cycling mechanisms for unlicensed LTE are being considered by the industry as a solution for channel management, the inherent time- and frequency-domain gaps in LTE transmissions render such mechanisms ineffective. Contrary to conventional wisdom, LTE contains such gaps and therefore fail to provide a continuous source of signal energy even during its active period. These gaps cannot be eliminated without specification changes. The size of the gaps is large enough for WIFI devices to misinterpret them as transmission opportunities, leading to collisions between WIFI and LTE frames during the LTE on-periods, rendering duty-cycling schemes ineffective.